Answer:
[tex]\boxed {\boxed {\sf molarity = 0.17 \ M \ C_6H_12O_6}}[/tex]
Explanation:
Molarity is found by dividing the moles of solute by liters of solution.
[tex]molarity = \frac {moles}{liters}[/tex]
We are given grams of a compound and milliliters of solution, so we must make 2 conversions.
1. Gram to Moles
We must use the molar mass. First, use the Periodic Table to find the molar masses of the individual elements.
Next, look at the formula and note the subscripts. This tells us the number of atoms in 1 molecule. We multiply the molar mass of each element by its subscript.
6(12.011)+12(1.008)+6(15.999)=180.156 g/mol
Use this number as a ratio.
[tex]\frac {180.156 \ g\ C_6H_12 O_6}{ 1 \ mol \ C_6H_12O_6}[/tex]
Multiply by the given number of grams.
[tex]78 \ g \ C_6H_12O_6 *\frac {180.156 \ g\ C_6H_12 O_6}{ 1 \ mol \ C_6H_12O_6}[/tex]
Flip the fraction and divide.
[tex]78 \ g \ C_6H_12O_6 *\frac { 1 \ mol \ C_6H_12O_6}{180.156 \ g\ C_6H_12 O_6}[/tex]
[tex]\frac { 78 \ mol \ C_6H_12O_6}{180.156 }= 0.432958102977 \ mol \ C_6H_12O_6[/tex]
2. Milliliters to Liters
There are 1000 milliliters in 1 liter.
[tex]\frac {1 \ L }{ 1000 \ mL}[/tex]
Multiply by 2500 mL.
[tex]2500 \ mL* \frac {1 \ L }{ 1000 \ mL}[/tex]
[tex]2500 * \frac {1 \ L }{ 1000 }= 2.5 \ L[/tex]
3. Calculate Molarity
Finally, divide the moles by the liters.
[tex]molarity = \frac {0.432958102977 \ mol \ C_6H_12O_6}{ 2.5 \ L}[/tex]
[tex]molarity = 0.173183241191 \ mol \ C_6H_12O_6/L[/tex]
The original measurement has 2 significant figures, so our answer must have the same. That is the hundredth place and the 3 tells us to leave the 7.
[tex]molarity \approx 0.17 \ mol \ C_6H_12O_6 /L[/tex]
1 mole per liter is also equal to 1 M.
[tex]molarity = 0.17 \ M \ C_6H_12O_6[/tex]
